// jpgd.h - C++ class for JPEG decompression.
// Public domain, Rich Geldreich <richgel99@gmail.com>
#ifndef JPEG_DECODER_H
#define JPEG_DECODER_H

#include <stdlib.h>
#include <stdio.h>
#include <setjmp.h>

#ifdef _MSC_VER
#define JPGD_NORETURN __declspec(noreturn)
#elif defined(__GNUC__)
#define JPGD_NORETURN __attribute__ ((noreturn))
#else
#define JPGD_NORETURN
#endif

namespace jpgd
{
    typedef unsigned char  uint8;
    typedef   signed short int16;
    typedef unsigned short uint16;
    typedef unsigned int   uint;
    typedef   signed int   int32;
    
    // Loads a JPEG image from a memory buffer or a file.
    // req_comps can be 1 (grayscale), 3 (RGB), or 4 (RGBA).
    // On return, width/height will be set to the image's dimensions, and actual_comps will be set to the either 1 (grayscale) or 3 (RGB).
    // Notes: For more control over where and how the source data is read, see the decompress_jpeg_image_from_stream() function below, or call the jpeg_decoder class directly.
    // Requesting a 8 or 32bpp image is currently a little faster than 24bpp because the jpeg_decoder class itself currently always unpacks to either 8 or 32bpp.
    unsigned char *decompress_jpeg_image_from_memory(const unsigned char *pSrc_data, int src_data_size, int *width, int *height, int *actual_comps, int req_comps);
    unsigned char *decompress_jpeg_image_from_file(const char *pSrc_filename, int *width, int *height, int *actual_comps, int req_comps);
    
    // Success/failure error codes.
    enum jpgd_status
    {
        JPGD_SUCCESS = 0, JPGD_FAILED = -1, JPGD_DONE = 1,
        JPGD_BAD_DHT_COUNTS = -256, JPGD_BAD_DHT_INDEX, JPGD_BAD_DHT_MARKER, JPGD_BAD_DQT_MARKER, JPGD_BAD_DQT_TABLE,
        JPGD_BAD_PRECISION, JPGD_BAD_HEIGHT, JPGD_BAD_WIDTH, JPGD_TOO_MANY_COMPONENTS,
        JPGD_BAD_SOF_LENGTH, JPGD_BAD_VARIABLE_MARKER, JPGD_BAD_DRI_LENGTH, JPGD_BAD_SOS_LENGTH,
        JPGD_BAD_SOS_COMP_ID, JPGD_W_EXTRA_BYTES_BEFORE_MARKER, JPGD_NO_ARITHMITIC_SUPPORT, JPGD_UNEXPECTED_MARKER,
        JPGD_NOT_JPEG, JPGD_UNSUPPORTED_MARKER, JPGD_BAD_DQT_LENGTH, JPGD_TOO_MANY_BLOCKS,
        JPGD_UNDEFINED_QUANT_TABLE, JPGD_UNDEFINED_HUFF_TABLE, JPGD_NOT_SINGLE_SCAN, JPGD_UNSUPPORTED_COLORSPACE,
        JPGD_UNSUPPORTED_SAMP_FACTORS, JPGD_DECODE_ERROR, JPGD_BAD_RESTART_MARKER, JPGD_ASSERTION_ERROR,
        JPGD_BAD_SOS_SPECTRAL, JPGD_BAD_SOS_SUCCESSIVE, JPGD_STREAM_READ, JPGD_NOTENOUGHMEM
    };
    
    // Input stream interface.
    // Derive from this class to read input data from sources other than files or memory. Set m_eof_flag to true when no more data is available.
    // The decoder is rather greedy: it will keep on calling this method until its internal input buffer is full, or until the EOF flag is set.
    // It the input stream contains data after the JPEG stream's EOI (end of image) marker it will probably be pulled into the internal buffer.
    // Call the get_total_bytes_read() method to determine the actual size of the JPEG stream after successful decoding.
    class jpeg_decoder_stream
    {
    public:
        jpeg_decoder_stream() { }
        virtual ~jpeg_decoder_stream() { }
        
        // The read() method is called when the internal input buffer is empty.
        // Parameters:
        // pBuf - input buffer
        // max_bytes_to_read - maximum bytes that can be written to pBuf
        // pEOF_flag - set this to true if at end of stream (no more bytes remaining)
        // Returns -1 on error, otherwise return the number of bytes actually written to the buffer (which may be 0).
        // Notes: This method will be called in a loop until you set *pEOF_flag to true or the internal buffer is full.
        virtual int read(uint8 *pBuf, int max_bytes_to_read, bool *pEOF_flag) = 0;
    };
    
    // stdio FILE stream class.
    class jpeg_decoder_file_stream : public jpeg_decoder_stream
    {
        jpeg_decoder_file_stream(const jpeg_decoder_file_stream &);
        jpeg_decoder_file_stream &operator =(const jpeg_decoder_file_stream &);
        
        FILE *m_pFile;
        bool m_eof_flag, m_error_flag;
        
    public:
        jpeg_decoder_file_stream();
        virtual ~jpeg_decoder_file_stream();
        
        bool open(const char *Pfilename);
        void close();
        
        virtual int read(uint8 *pBuf, int max_bytes_to_read, bool *pEOF_flag);
    };
    
    // Memory stream class.
    class jpeg_decoder_mem_stream : public jpeg_decoder_stream
    {
        const uint8 *m_pSrc_data;
        uint m_ofs, m_size;
        
    public:
        jpeg_decoder_mem_stream() : m_pSrc_data(NULL), m_ofs(0), m_size(0) { }
        jpeg_decoder_mem_stream(const uint8 *pSrc_data, uint size) : m_pSrc_data(pSrc_data), m_ofs(0), m_size(size) { }
        
        virtual ~jpeg_decoder_mem_stream() { }
        
        bool open(const uint8 *pSrc_data, uint size);
        void close() { m_pSrc_data = NULL; m_ofs = 0; m_size = 0; }
        
        virtual int read(uint8 *pBuf, int max_bytes_to_read, bool *pEOF_flag);
    };
    
    // Loads JPEG file from a jpeg_decoder_stream.
    unsigned char *decompress_jpeg_image_from_stream(jpeg_decoder_stream *pStream, int *width, int *height, int *actual_comps, int req_comps);
    
    enum
    {
        JPGD_IN_BUF_SIZE = 8192, JPGD_MAX_BLOCKS_PER_MCU = 10, JPGD_MAX_HUFF_TABLES = 8, JPGD_MAX_QUANT_TABLES = 4,
        JPGD_MAX_COMPONENTS = 4, JPGD_MAX_COMPS_IN_SCAN = 4, JPGD_MAX_BLOCKS_PER_ROW = 8192, JPGD_MAX_HEIGHT = 16384, JPGD_MAX_WIDTH = 16384
    };
    
    typedef int16 jpgd_quant_t;
    typedef int16 jpgd_block_t;
    
    class jpeg_decoder
    {
    public:
        // Call get_error_code() after constructing to determine if the stream is valid or not. You may call the get_width(), get_height(), etc.
        // methods after the constructor is called. You may then either destruct the object, or begin decoding the image by calling begin_decoding(), then decode() on each scanline.
        jpeg_decoder(jpeg_decoder_stream *pStream);
        
        ~jpeg_decoder();
        
        // Call this method after constructing the object to begin decompression.
        // If JPGD_SUCCESS is returned you may then call decode() on each scanline.
        int begin_decoding();
        
        // Returns the next scan line.
        // For grayscale images, pScan_line will point to a buffer containing 8-bit pixels (get_bytes_per_pixel() will return 1).
        // Otherwise, it will always point to a buffer containing 32-bit RGBA pixels (A will always be 255, and get_bytes_per_pixel() will return 4).
        // Returns JPGD_SUCCESS if a scan line has been returned.
        // Returns JPGD_DONE if all scan lines have been returned.
        // Returns JPGD_FAILED if an error occurred. Call get_error_code() for a more info.
        int decode(const void** pScan_line, uint* pScan_line_len);
        
        inline jpgd_status get_error_code() const { return m_error_code; }
        
        inline int get_width() const { return m_image_x_size; }
        inline int get_height() const { return m_image_y_size; }
        
        inline int get_num_components() const { return m_comps_in_frame; }
        
        inline int get_bytes_per_pixel() const { return m_dest_bytes_per_pixel; }
        inline int get_bytes_per_scan_line() const { return m_image_x_size * get_bytes_per_pixel(); }
        
        // Returns the total number of bytes actually consumed by the decoder (which should equal the actual size of the JPEG file).
        inline int get_total_bytes_read() const { return m_total_bytes_read; }
        
    private:
        jpeg_decoder(const jpeg_decoder &);
        jpeg_decoder &operator =(const jpeg_decoder &);
        
        typedef void (*pDecode_block_func)(jpeg_decoder *, int, int, int);
        
        struct huff_tables
        {
            bool ac_table;
            uint  look_up[256];
            uint  look_up2[256];
            uint8 code_size[256];
            uint  tree[512];
        };
        
        struct coeff_buf
        {
            uint8 *pData;
            int block_num_x, block_num_y;
            int block_len_x, block_len_y;
            int block_size;
        };
        
        struct mem_block
        {
            mem_block *m_pNext;
            size_t m_used_count;
            size_t m_size;
            char m_data[1];
        };
        
        jmp_buf m_jmp_state;
        mem_block *m_pMem_blocks;
        int m_image_x_size;
        int m_image_y_size;
        jpeg_decoder_stream *m_pStream;
        int m_progressive_flag;
        uint8 m_huff_ac[JPGD_MAX_HUFF_TABLES];
        uint8* m_huff_num[JPGD_MAX_HUFF_TABLES];      // pointer to number of Huffman codes per bit size
        uint8* m_huff_val[JPGD_MAX_HUFF_TABLES];      // pointer to Huffman codes per bit size
        jpgd_quant_t* m_quant[JPGD_MAX_QUANT_TABLES]; // pointer to quantization tables
        int m_scan_type;                              // Gray, Yh1v1, Yh1v2, Yh2v1, Yh2v2 (CMYK111, CMYK4114 no longer supported)
        int m_comps_in_frame;                         // # of components in frame
        int m_comp_h_samp[JPGD_MAX_COMPONENTS];       // component's horizontal sampling factor
        int m_comp_v_samp[JPGD_MAX_COMPONENTS];       // component's vertical sampling factor
        int m_comp_quant[JPGD_MAX_COMPONENTS];        // component's quantization table selector
        int m_comp_ident[JPGD_MAX_COMPONENTS];        // component's ID
        int m_comp_h_blocks[JPGD_MAX_COMPONENTS];
        int m_comp_v_blocks[JPGD_MAX_COMPONENTS];
        int m_comps_in_scan;                          // # of components in scan
        int m_comp_list[JPGD_MAX_COMPS_IN_SCAN];      // components in this scan
        int m_comp_dc_tab[JPGD_MAX_COMPONENTS];       // component's DC Huffman coding table selector
        int m_comp_ac_tab[JPGD_MAX_COMPONENTS];       // component's AC Huffman coding table selector
        int m_spectral_start;                         // spectral selection start
        int m_spectral_end;                           // spectral selection end
        int m_successive_low;                         // successive approximation low
        int m_successive_high;                        // successive approximation high
        int m_max_mcu_x_size;                         // MCU's max. X size in pixels
        int m_max_mcu_y_size;                         // MCU's max. Y size in pixels
        int m_blocks_per_mcu;
        int m_max_blocks_per_row;
        int m_mcus_per_row, m_mcus_per_col;
        int m_mcu_org[JPGD_MAX_BLOCKS_PER_MCU];
        int m_total_lines_left;                       // total # lines left in image
        int m_mcu_lines_left;                         // total # lines left in this MCU
        int m_real_dest_bytes_per_scan_line;
        int m_dest_bytes_per_scan_line;               // rounded up
        int m_dest_bytes_per_pixel;                   // 4 (RGB) or 1 (Y)
        huff_tables* m_pHuff_tabs[JPGD_MAX_HUFF_TABLES];
        coeff_buf* m_dc_coeffs[JPGD_MAX_COMPONENTS];
        coeff_buf* m_ac_coeffs[JPGD_MAX_COMPONENTS];
        int m_eob_run;
        int m_block_y_mcu[JPGD_MAX_COMPONENTS];
        uint8* m_pIn_buf_ofs;
        int m_in_buf_left;
        int m_tem_flag;
        bool m_eof_flag;
        uint8 m_in_buf_pad_start[128];
        uint8 m_in_buf[JPGD_IN_BUF_SIZE + 128];
        uint8 m_in_buf_pad_end[128];
        int m_bits_left;
        uint m_bit_buf;
        int m_restart_interval;
        int m_restarts_left;
        int m_next_restart_num;
        int m_max_mcus_per_row;
        int m_max_blocks_per_mcu;
        int m_expanded_blocks_per_mcu;
        int m_expanded_blocks_per_row;
        int m_expanded_blocks_per_component;
        bool  m_freq_domain_chroma_upsample;
        int m_max_mcus_per_col;
        uint m_last_dc_val[JPGD_MAX_COMPONENTS];
        jpgd_block_t* m_pMCU_coefficients;
        int m_mcu_block_max_zag[JPGD_MAX_BLOCKS_PER_MCU];
        uint8* m_pSample_buf;
        int m_crr[256];
        int m_cbb[256];
        int m_crg[256];
        int m_cbg[256];
        uint8* m_pScan_line_0;
        uint8* m_pScan_line_1;
        jpgd_status m_error_code;
        bool m_ready_flag;
        int m_total_bytes_read;
        
        void free_all_blocks();
        JPGD_NORETURN void stop_decoding(jpgd_status status);
        void *alloc(size_t n, bool zero = false);
        void word_clear(void *p, uint16 c, uint n);
        void prep_in_buffer();
        void read_dht_marker();
        void read_dqt_marker();
        void read_sof_marker();
        void skip_variable_marker();
        void read_dri_marker();
        void read_sos_marker();
        int next_marker();
        int process_markers();
        void locate_soi_marker();
        void locate_sof_marker();
        int locate_sos_marker();
        void init(jpeg_decoder_stream * pStream);
        void create_look_ups();
        void fix_in_buffer();
        void transform_mcu(int mcu_row);
        void transform_mcu_expand(int mcu_row);
        coeff_buf* coeff_buf_open(int block_num_x, int block_num_y, int block_len_x, int block_len_y);
        inline jpgd_block_t *coeff_buf_getp(coeff_buf *cb, int block_x, int block_y);
        void load_next_row();
        void decode_next_row();
        void make_huff_table(int index, huff_tables *pH);
        void check_quant_tables();
        void check_huff_tables();
        void calc_mcu_block_order();
        int init_scan();
        void init_frame();
        void process_restart();
        void decode_scan(pDecode_block_func decode_block_func);
        void init_progressive();
        void init_sequential();
        void decode_start();
        void decode_init(jpeg_decoder_stream * pStream);
        void H2V2Convert();
        void H2V1Convert();
        void H1V2Convert();
        void H1V1Convert();
        void gray_convert();
        void expanded_convert();
        void find_eoi();
        inline uint get_char();
        inline uint get_char(bool *pPadding_flag);
        inline void stuff_char(uint8 q);
        inline uint8 get_octet();
        inline uint get_bits(int num_bits);
        inline uint get_bits_no_markers(int numbits);
        inline int huff_decode(huff_tables *pH);
        inline int huff_decode(huff_tables *pH, int& extrabits);
        static inline uint8 clamp(int i);
        static void decode_block_dc_first(jpeg_decoder *pD, int component_id, int block_x, int block_y);
        static void decode_block_dc_refine(jpeg_decoder *pD, int component_id, int block_x, int block_y);
        static void decode_block_ac_first(jpeg_decoder *pD, int component_id, int block_x, int block_y);
        static void decode_block_ac_refine(jpeg_decoder *pD, int component_id, int block_x, int block_y);
    };
    
} // namespace jpgd

#endif // JPEG_DECODER_H